Centrifugal pump.



J. L. GOKER, JR. GENTRIFUGAL PUMP.

APPLICATION FILED DBO. 9,1910.

2 sHnnTHsHnET 1.

Patented July 25 fiwamwz' Jwmz. 60%; 7:

J. L. (JOKER, JR. GENTRIFUGAL PUMP.

APPLICATION FILED DEC. 9, 1910.

Patnted July 25, 1911.

2 SHEETS-SHEET 2.

JAMES L. COKER, 13., OF HABTSVILLE, SOUTH CAROLINA.

' CENTRIFUGAL PUMP.

Specification of Letters Patent.

Application filed December 9, 1910 Patented July 25 1911. Serial No.596,515.

To all whom it may concern:

\ Be it known that 1, JAMES L. COKER, J r., a citizen of the UnitedStates, and a resident of Hartsville, in the county of Dar- 5lin gtonand State of South Carolina, have invented certain new and usefulImprovements in Centrifugal Pumps, of which the following is aspecification.

This invention is designed to produce a centrifugal pump of highefliciency, with which. end in view its primary object is to wobtainuniform acceleration of velocity of the intake water along the shortestand smoothest practical'path between the inner and outer circles whichbound the annular runway wherein the impeller or runner blades areincluded.

My invention resides in the means hereinafter set forth whereby thisobject is accomplished, and refers particularly to the shapeandconfiguration of the runner blades and the annular runway in whichsaid blades move.

i I shall first describe in connection with the accompanying drawingsthe best way now known to me of carrying my improvements into practicaleffect, and will then point out more particularly in the claims thosefeatures which I believe to be new and of my own invention.

In said drawings-Figure 1 is a side elevation of a centrifugal pumpembodying my invention, with a portion of the case removed to enable meto better illustrate the manner of laying'out the runner blades. Fig. 2is atop plan, half in axial section. These twofigures are largelydiagrammatic, and are intended more particularly to indicate graphicallythe method of desi i0 those portions of the pumpto whic my inventionrelates. Fig. 3 is an axial section on a larger scale of somuch of apump as will show a cross section of the annular runway, together with aview of one of the runner blades therein. Fig. 4 is a longitudinalsection of one of the blades, this section being on the median line ofthe blade. Figs. 5, 6, 7, 8, are cross sections of the blade on lines 556-6, 7-7, and 88, respectively .50'of Fig. 4. In each of these figuresis-also shown a portion of the runner to which the blade at one edge isattached.

The problem is to increase the velocity of the intake water by uniformacceleration along the shortest and smoothest practical path fromv theinner to the outer circle of ing . discharge pipes.

i the impeller blades. This path may be normal to, or in someinstances-as for example in high l1ft or high revolution pumpsmake anangle with, the inner circle of the blades,

but with the outer circle of the blades it.

should make the least possible angle. The

acquired velocity of the water in this path, when it reaches the outercircle of the blades, should equal that due to the total head againstwhich the pump is 'to WOI'k. After passing the outer circle of the'blades the water should still follow'a smooth, continuous path withuniform retardation to a velocity corresponding to that of the dischargepipe. v F

The single-side intake pump, because of its lower cost of construction,is to be pre ferred where the degree of pull or suction necessary tobring the water to the pump is not large, and also where the headagainst which the pump operates is small. Such a pump is illustrated inthe drawings; where- 1n, so far as the general constructlon isconcernedreferring more particularly to Figs. 1 and 2it is suflicient tosay that, 1 is the scroll pump casing having intake 2-and discharge pipeP; 3 is the runner .disk mounted as usual upon a rotary power drivenshaft passing through a stufling'box in one head of the pump casing; 4are the impeller blades; and 5 and 6 are the inner and outer circlesrespectively of said blades.

The flow of water along the paths and. with the velocities abovereferred to is secured by maintaining suitable relations be tween theform of pump casing and blade and speed of runner, the method pursuedbeing as follows:

I. Knowing the quantity of water to be handled and the head againstwhich it is to be lifted, the first step in the designing w1ll be todetermine the sizes of the intake and ation is the main considerationthe velocity of flow of water in the intake pipe should not exceedsubstantially 6 feet per second for ordinary suction lengths, and thevelocity in the discharge pipe should range be tween 7 feet and 12 feetper second. The

diameters for these pipes will be determined by the equation E 1 6O 12 V7r q Where Q, is quantity in gallons per minute and V is given a valueclose to the limits.

Whereeconomy of operior having reference more particularly to the weobtain a value of 8 inches for diameter of intake pipe. 80, also, we geta value of 7 inches for diameter of discharge pipe'by giving V, at thatpoint, a value of approximately 8.3 feet per second in the sameequation.

II. In determining the size of the runner,

diameters of the intake and outer circles 5 and6, between which theimpeller blades are included, the source of motive power operating thepump must be considered; for the outside diameter will vary inverselywith the speed of rotation ofvthe runner, and directly with the quantityof water to be handled.

' Where practical, the tangential velocity of the outer edge of theblade should conform to that due to the head against which the pump isto operate. From one or moretent'ative layouts, depending upon theforegoing considerations, upon a path of acceleration (shown at A-E,Fig. 1) assumed on the principle hereinbefore referred to, and upon thediameter of the intake 7 pipe, definitevalues may be determined for theinnerand outer circles. For example, in the pump illustrated in thediagram the head against which it is to operate is 9 feet.

From any manual of engineering we find V :2gh, where V is the velocityacquired by a body falling from a height h, g is velocity due to gravityacting for one second, and

.h is height, o yin hydraulics, head. Substituting 9 for h, and solving,we have V= /64 9=24 (feet per second) approximately, which is the propervelocity for the outer tip of blade.

- Assuming the pump is to be belt driven, a convenient size of runnerwill be one hav-. ing an outer blade circle, 6, of 15.4 inches diameteror about 48 inches in circumference, thus requiring a speed of rotationfor the runner of 360 revolutions per minute to accomplish the requiredtangential speed at 24 feet per second of the outer edges or tips of theblades.

ciently taken as 8.5 inches, this figure being controlled by thediameter of the intake pipe in connection with the curve of entrance at-V, Fig. 2, which should be tangent to the The diameter of the intakecircle 5, under these conditions, may be effiside of the intake pipe,and also to the curve of the annular space of the case wherein theimpeller blades operate. The circles 5 and 6 bound the throat or runwayin which the impeller blades move.

III. The circumferences of these circles being known, together with theradial velocity and quantity passing through the pump, the widths ofsaid throat or runway on the circles 5 and 6 are obtained by theequation- Q 231 60 12 V C 2) in which w:width of throat in inches; Q:quantity of water in gallons 'per minute; V :radial component ofvelocity in feet per second; C circumference in inches of that-particular blade circle under consideration. The width of the throat orrunway at these circles is indicated in Fig. 2 by the ordinates V Y andVi -X respectively. Applying this equation (Eq. 2) to the pumpillustrated in Fig. 2, and assuming frictional losses in the intake pipewill result in the water arriving at the intake circle 5 at an actualvelocity of 6 feet per second along a path normal to that circle and inplanes perpendicular to the axis of rotation of the. runner, then,substituting known .values in Eq 2, and solving, we get 2 approximately,

6. The length of the ordinates at other sec tions of the throat, as at B0 ,13 Fig. 2, depends upon the acceleration curve AE, (Fig. 1); and of"Ehe ordinates beyond the outer circle 6, as at F, G H K upon theretardation curve E-K (Fig. l)-the latter being a continuation of theformer. These two curves are determined in the tentative lay out, andmay be arcs of mathematical spirals, or a series of arcs of circlessmoothly joined, thecurves themselves being governed at theirextremities by the consideration that they must be smooth and continuousat E where they join; also that the acceleration curve should ,be normalto the intake circle, but should make the smallest possible angle withthe outer circle; and that the retardation curve must discharge at suchan angle-that the radial component of velocity of the water will givepractical and suitable dimensions for the interior of the pump casing onthe circular section at N K, Fig. 1. It may be here remarked, that thecircle -in Fig. 1 on which N and K are located is diagrammatic andrepresentative of the outer boundary of the annular spacebetween E andN, Fig. 1, corresponding to the retarding section between-E and K Fig.2.

In the design illustrated in Figs. 1 and 2, the acceleration curve makeswith the outer circle 6 an angle whose natural tangent is :radialcomponent of velocity C M may be found, and the width of throatcorresponding to the ordinate at C Fig. 2, determined for the sectionthrough C by the use of Eq. 2, as above. In a similar manner, as manypoints as desired may be found from A to K. To obtain the various pointson the curves for computing these sections, it is convenient to dividethe curves on a time basis, it requiring the same length of time for aparticle of water to flow from A to B as from B to C, and so on. Toobtain these division points, use is made of the formulas V =2aS+V (Eq.3)

V at+V (Eq. 4)

in whichV :velocity of water along path at E; V :velocity of water alongpath at A; (L -acceleration in feet per second, per second; S length ofpath A' E in feet; t z

time in seconds required for Water to pass from A to E.

In Equation 3, allqua'ntities are known except a. Its value is found andsubstituted in Equation 4, thus giving the actualtime fora particle ofwater to pass from A to E, while traveling in the mid-plane A K Fig. 2.There would naturally be slight variations for particles moving alongthe curved walls V --W and Y X of the throat or runwa'y on either sideof the midplanefwhich variations may be compensated for as indicatedlater. 7 The total time required for water to pass from A to E may bedivided, as hereinbefore indicated, into a convenient number of equalpartsin this instance four, represented by the spaces AB, B C, C-D, DE..The velocity of water along path at A and E has been already assumed.Like values at B, C, D may be obtained at these times by the use ofEquation 4, giving 25 in that equation its appropriate value. The

values V ,etc.,having been thus ascertained,

are then substituted for V in Equation 3,

'and S found and laid off from A to B, A to C, etc. As before stated,similar points F, G, H, on the retardation curve, between E and K, andcorresponding ordinates F, G,

H (Fig. 2), can be computed on the same principle as for B,.C, D, and B0, D

IV. Knowing the revolutions per minute of the runner (360) and the timerequired for a particle of water to move from A to E, it is readilyfound how far the inner tip of the impeller blade will move in the sametime. This distance is A e and is equal'to rpm. X 21:13,

i (Eq.4) x

C-D, etc., are assumed to be traversed in equal times by a particle ofwater, the equally spaced points 6, 0, cl, etc., (Fig. 1) will representthe position of the inner tip of air impeller blade when the Waterparticle is at B, C, D, etc., both having passed the point A at thesametime.

\From these data, the form of impeller blade can be convenientlyobtained as follows: On a piece of tracing cloth placed on the. drawing,Fig, 1, and pivoted to rotate about, 0 as a center, mark a point A, (notshown) directly over A, Fig. 1; then rotate the cloth until its point Ais directly over I), and directly over 'B in the drawing, mark a point Bon the tracing cloth; do also the same at 0, (Z and e, and there will beobtained on the tracing cloth a series of.

points A 'E which, when connected, will give a form of blade-4nlongitudinal edge e view-similar to the form of blade E c, Fig. 1.. "Theform thus obtained should check with the velocity construction shown atc, f, g, h, in which e-f represents velocity of tip of impeller bladeand eg velocity of particle of water at e, both'in feet per second, thusgiving the resultant velocity e17z relative to the runner. A tangent tothe blade at e should coincide with thisresultant eh, to insure theabsence of shock at the point e.' Should there be lack of coinci dencehere, some changes in the assumptions mustbe'made, as for example in thewater path "AE, until the two constructions agree.

It will be noted that the impeller blade,

as shown in the diagrammatic Figs. 1 and 2,

inclines rearwardly relatively to the direc- .tion of revolution of therunner (indicated by the arrow in Fig. 1) and is narrower at ness ofblades may be made by considering an increase in the diameter of theintake circle 5, and also by an increase in the ord 1-' nates, as at A BG etc.; modifications 1n the values of the affected terms in theequations hereinbefore given should be made accordingly.

Since the foregoing computations are theoretically true only forparticles of water flowing in the median plane A -K Fig. 2, modificationof the form of the impeller blade may be made to vary its longitudinalcontour slightly from that represented by the line 6 E, Fig. 1, to thatrepresented by dotted lines V W in the same figure, this modificationbeing obtained by erecting curved ordinates normal to the direction offlow of particles not in the median plane, instead of the straightordinates at A, B etc., Fig. 2. Also, according to the action of thewater in flow, the form of the blade at the inner and outer extremitiesmay be varied from straight lines as shown .in Figs. 1

and 2, to curved lines. These modifications are desirable as tending toinsure uniform acceleration of all the particles of water, but in manycases are practically negligible, their importance for a given size ofrunner increasing with the increased quantity of water to be handled. InFigs. 3 and 4, etc., I have shown an impeller blade 4 which embodies allthese features. The throat or runway in Fig. 3 varies somewhat in formand dimensions from that shown in Fig. 1; but this is not material asconcerns the present purpose. It will be noted that the blade has thelongitudinal forward curvature 7 of its outer end which characterizesthe blade graphically indicated at E c, Fig. 1. The edges of its twoends have a slight lengthwise curv'ature as indicated at 8, 9, Fig. 3;

its inner end has a transverseconcave for-" mation 10, which graduallydiminishes in depth and finally vanishes as it approaches thelongitudinal center of the blade, as indicated in Figs. 4, 5 and 6; itsouter end, which has the forward curvature 7, hereinbefore referred to,is also curved transversely, having a convex formation, .11, which ispractically confined to the forwardly curved part 7 and'decreases as itrecedes from the outer end of the blade until it finally vanishes. Thesecurves 8, 9, 10, 11, as before saidfwhile desirable are notindispensable.

The lengthwise transverse dimensions of the blade are clearly indicatedin Figs. 58. It is narrowest at a point between its ends as .indicatedin Fig. 7 ,and thence, as indicated in Figs. 5, 6, 8, graduallyincreases in width toward each end, its edges conforming to thecurvature of that portion of the opposed walls of the runway betweenwhich it isineluded. p

The curve through R, S, T, etc.,.Fig. l, is

'work in high-lift and in" double-intake the usual spiral water way,which should be proportioned so that sections K R etc.,

Fig. 2, will pass their proportionate amount of water on its way to thedischarge pipe P.

The fin Z, Fig. 1, is formed on such a construction line as will givethe best division of the two streams, one making for the discharge pipe,and the other for the spiral circuit. In obtaining the form of bladesand the channels by the process herein set forth, suitable allowance, ofcourse, must be made for friction values.

The principles of construction here involved apply to double intake,aswell as to the single intake which is here illustrated.

'In this particular pump the intake water is given a radial direction offiow in the midplane of the blade and atthe inner tip of the blade, butthis is not an essential feature, as the water may be taken to haveaflow at any initial angle, and the design worked out accordingly alongthe linesfherein specified. This initial angle maybe necessary for bestpumps, and may be established by a suitable shape of intake opening orby directing vanes. i

As before pointed out, the blades while inclined rearwardly from thepoint of intake, have at the same time a forward curvature at theirouter ends. I remark that this our vature is not arbitrary, but may, andwill, be of greater or less extent, according to the varying factors ofthe problem.

Where the water to be handled contains solid matter in suspension, suchas strings, chips, gravel, etc., the impeller blades should be strongerthan forpure water, and should extend past the intake circle toward thecenter of the runner, to prevent clogging- Having described myimprovements and the best way now known to me of carrying the same intopractical effect, I state in con clusion that I do not limit myselfstrictly to the structuraldetails herein illustrated, since manifestlythe same can be varied in a num ber of particulars without departurefrom my invention: but

What I claim as new and of my own invention is asfollows:v

1. The combination with the pump casing and runner, of impeller bladesnarrowest at a point between their ends and thence graduallyincreasingin width toward each end,

secured to the runner and inclined rearwardly from the point of intake,and an annular throat or runway in. the casing for said blades, havingopposed faces convex in cross section and of a contour to conform to"the longitudinal concave edges of the blades in the position which theyoccupy in the run-- way, substantially as and for the purposehereinbefore set forth. I i

2. The combination with the pump cas-' t0 the longitudinal concave edgesof the ing and runner, of impeller blades carried blades in the positionwhich they occupy in by the runner, narrowest at a point between therunway, substantially as and for the their ends and thence graduallyincreasing purposes hereinbefore set forth. 3

5 in width toward each end, inclined rear- In testimony whereof I afiixmy signa- 15 Wardly from the point of intake, and having ture inpresence of two witnesses. a forward curvature at their outer ends, andJAMES L. COKER, J R. an annular throat or runway in the casingWitnesses: for said blades, having opposed faces convex JOHN L.FLETCHER,

10 in cross section and of a contour to conform .V. LEE HELMS.

